Exciting Electrons

RubyLake1F
Posts: 41
Joined: Fri Apr 06, 2018 11:03 am

Exciting Electrons

Question 2.33 in the homework is this:
Which of the following increase when an electron in a lithium atom undergoes a transition from the 1s-orbital to a 2p-orbital? (a) Energy of the electron. (b) Value of n. (c) Value of l. (d) Radius of the atom. Compare your answers to the answers to Exercise 2.1 and explain any differences.

And for part d) I thought the answer might be 'stays the same' because the atom already has a second shell, so this transition wouldn't add a new shell to the atom- but I checked and the book says the radius of the atom will increase. Is this because the p orbital extends farther out than the S orbital? Would there ever be a case where an electron could be excited up to a higher energy level without increasing the radius of the atom (eg. would radius increase if electron was excited from 1s to 2s in Lithium)?

Beverly Shih 1K
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Joined: Wed Nov 15, 2017 3:01 am
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Re: Exciting Electrons

When the electron goes from 1s to 2p, its principal quantum number (n) goes from 1 to 2, meaning it goes from the first shell to the second shell. The shell directly corresponds to the size of the orbital, so a higher value of n means a larger size of atom.

Mei Blundell_1J
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Joined: Fri Apr 06, 2018 11:01 am
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Re: Exciting Electrons

Yes, and if the electrons are being added to the same shell (as in moving across the periodic table) then the radius of the atom actually decreases because the electrons are being pulled in by increased effective nuclear charge.